Scientists determined the exact date of construction of the Por-Bazhin fortress in the Republic of Tuva. They used a new method that combines the analysis of radiocarbon and dendrochronology, as well as taking into account the “Miyake experience”. The article on this was published in the Proceedings of the National Academy of Sciences journal.
Por-Bazhin is a fortress in the south of Tuva, which occupies the entire island of Lake Tere-Khol, bordering Mongolia. Archaeologists associate it with the Uyghur Khanate, which in the VIII-IX centuries occupied the southern part of Siberia and modern Mongolia.
The controversy over the date of construction of this building has been lasting for many years. However, the results of radiocarbon-based analysis allowed to make definite conclusions. Researchers studied the cut trunks of three cedar trees built at the bottom of the mud walls of Por-Bazhin.
During the existence of the Uyghur khanate there was a period called the “Miyake experience”. In 2012, a team of Japanese scientists led by Fusa Miyake analyzed the content of radioactive carbon -14 in the annual rings of cedar and found an enhanced growth in 775. Scientists attribute this to the intense glare of the sun. Subsequent studies have confirmed that in 775, an increase in the amount of carbon-14 in the annual rings of trees was observed in other parts of the world. He also discovered that there were several similar incidents in the first millennium AD.
A team of scientists led by Margot Keitems of the University of Groningen (Netherlands) used a method that takes into account the “Miyake experiences” to determine the date of the Por-Bazhin fortress. The researchers performed radiocarbon analysis of 20 samples of logs from Por-Bazhin and found high levels of carbon-14, indicating the “Miyake experience” of 775. After that, it was enough to count the next rings to determine the year of felling of trees. Local building materials – cedar that grows on the Tere-Khol Lake – were widely used in the construction of Por-Bazhin. According to this, scientists concluded that the trees were cut down for special construction and dried in summer.
Researchers believe that Por-Bazhin was built in the summer of 777, during the reign of the Uyghur khagan Bogu, as a Manichaean temple.